MONDAY, Nov. 3 (HealthDay News) -- Researchers have detected abnormalities in the brains of people with fibromyalgia, a complex, chronic condition characterized by muscle pain and fatigue.

"We showed in our study that the functional abnormalities observed were mainly related to disability," and not to anxiety and depression status, said Dr. Eric Guedj, the study's lead author and a researcher at Centre Hospitalier-Universitaire de la Timone in France.

While some researchers have suggested that the pain reported by fibromyalgia patients was the result of depression, the new study suggests otherwise. The abnormalities found on brain scans done by the study authors were independent of the women's anxiety and depression levels, Guedj said.

The French researchers evaluated 20 women diagnosed with fibromyalgia and 10 healthy women without the condition who served as a control group. They asked all the women to respond to questionnaires to determine levels of pain, disability, anxiety and depression.

Then, the researchers performed brain imaging called single photon emission computed tomography, or SPECT.

The imaging showed that women with the syndrome had "brain perfusion" -- or blood flow abnormalities -- compared to the healthy women. The researchers then found that these abnormalities were directly correlated with the severity of disease symptoms.

An increase in blood flow was found in the brain region known to discriminate pain intensity, the researchers found.

The findings were published in the November issue of The Journal of Nuclear Medicine.

An estimated 10 million Americans are thought to have fibromyalgia, the majority of them women, according to the National Fibromyalgia Association. They report a history of widespread pain in all four quadrants of the body for at least three months, and pain in at least 11 of 18 "tender points."

The cause of fibromyalgia remains a mystery, according to the association, but it may occur following physical trauma such as an injury, experts say. Treatments focus on relieving symptoms and helping patients function.

In previous research, Guedj and his team had found functional abnormalities in areas of the brain of fibromyalgia patients. The latest study goes a step further, demonstrating that the brain abnormalities are correlated with disease severity, he said.

Dr. Patrick Wood, senior medical adviser for the National Fibromyalgia Association, said the new study provides "further evidence of an objective difference between patients with fibromyalgia and those who don't have the disorder." Wood reviewed the study results but was not involved with the research.

Other studies have found a correlation between brain abnormalities and fibromyalgia symptoms, Wood said, adding that the new study adds more evidence and information on how the abnormalities affect patients.